There is much disclosed and written about the joining of materials together and particularly metals through various welding techniques. Some techniques make use of chemical means, others look to the use of heat and still others involve ultrasonic devices. Some examples of such devices and methodology are found in U.S. Pat. Nos., 4,037,078; 4,368,371; 4,591,687; and 5,082,160. The present invention and method is quite different. Joinder is accomplished by shooting a projectile partially through the metals to be joined.
Looking to the joining or welding of aluminum or its alloys, there is the issue of the formation of "hot tears". The "hot tear" effect manifests itself in the form of a crack generated behind the solid front of a weld.
To understand this situation, one must look to the make-up of the metal. The crystallograins of weld metal will assume the orientation of the parent seed crystal adjacent to the fusion zone even though competitive growth between grains will exist owing to the relationship between preferred growth directions and the thermal gradients in the weld pool. The nucleation of new grains with more favorable orientations is seldom observed in the absence of heterogenous nuclei.
Prior art improvements have been achieved in the weldability of metals and in particular aluminum and its alloys. This has been accomplished largely by refinement of the weld metal grain size by adding an element which will provide some type of substrate upon which new grains of weld metal can form. Unfortunately, the prior art is anything but conclusive as to the relationship between usable intermetallic inclusions in the welding consumable, such as the welding wire, and the process of manufacturing the consumable. Similarly, the prior art is silent on the sensitivity of the intermetallic inclusions in the consumable to the thermodynamics of the weld itself.
It is believed that the present invention addresses these issues by presenting a process which may be used with or without electrical power. More precisely, the present invention operates without the application of heat to the projectile or the material to be welded.